Structure and Composition of Riparian Boreal Forest: New Methods for Analyzing Edge Influence
Abstract:
Riparian ecotones at lakeshore edges are prominent features on the hetero-geneous boreal forest landscape. We introduce a new method (the critical values approach),which incorporates inherent variability in interior forest, to quantify distance of edge in-fluence at lakeshore forest edges. We use this method to examine the variation in foreststructure and composition along the lakeshore forest edge-to-interior gradient in the mixed-wood boreal forest. Our objectives were: (1) to quantify distance of edge influence forforest structure and composition at lakeshore forest edges; and (2) to investigate spatialpattern in vegetation along the edge-to-interior gradient. Trees, coarse woody material,saplings, shrubs, and herbs were sampled in plots at varying distances along 200-m transectsestablished perpendicular to lakeshore forest edges. Distance of edge influence was deter-mined by comparing mean values at different positions along the transect to critical valuesestablished from a randomization test of interior forest data. The spatial pattern of fourselected species along the edge-to-interior gradient was assessed using split moving windowanalysis and wavelet analysis. The results suggest that a distinct lakeshore forest edgecommunity exists. This community was;40 m wide and was characterized by greaterstructural diversity, larger amounts of coarse woody material, and more saplings and mid-canopy trees than interior forest. Distance of edge influence for understory compositionwas generally greater than for forest structure. Patterns of response for different speciesalong the edge-to-interior gradient were related to shade tolerance. Lakeshore forest edgesare distinct landscape elements, but their prominence depends on the reference forest,species, and scale.
Authors: K. A. Harper and S. E. MacDonald
Riparian ecotones at lakeshore edges are prominent features on the hetero-geneous boreal forest landscape. We introduce a new method (the critical values approach),which incorporates inherent variability in interior forest, to quantify distance of edge in-fluence at lakeshore forest edges. We use this method to examine the variation in foreststructure and composition along the lakeshore forest edge-to-interior gradient in the mixed-wood boreal forest. Our objectives were: (1) to quantify distance of edge influence forforest structure and composition at lakeshore forest edges; and (2) to investigate spatialpattern in vegetation along the edge-to-interior gradient. Trees, coarse woody material,saplings, shrubs, and herbs were sampled in plots at varying distances along 200-m transectsestablished perpendicular to lakeshore forest edges. Distance of edge influence was deter-mined by comparing mean values at different positions along the transect to critical valuesestablished from a randomization test of interior forest data. The spatial pattern of fourselected species along the edge-to-interior gradient was assessed using split moving windowanalysis and wavelet analysis. The results suggest that a distinct lakeshore forest edgecommunity exists. This community was;40 m wide and was characterized by greaterstructural diversity, larger amounts of coarse woody material, and more saplings and mid-canopy trees than interior forest. Distance of edge influence for understory compositionwas generally greater than for forest structure. Patterns of response for different speciesalong the edge-to-interior gradient were related to shade tolerance. Lakeshore forest edgesare distinct landscape elements, but their prominence depends on the reference forest,species, and scale.
Authors: K. A. Harper and S. E. MacDonald